Ah, it's nice to work at a university were access to journals is so easy.
One thing that was interesting to note was that the coloring is a sex-linked trait. The gene is linked to the Z chromosome, and in birds, females are ZW and males are ZZ, so females only get one copy of the gene, and males get two. Red is dominant (also weird, i thought) to black. But none of this is the really interesting stuff
For those that want some solid numbers:
Genetically incompatible (red with black) pairs have 40.2% greater mortality of sons and 83.8% greater mortality of daughters than brood produced from genetically compatible (red-red or black-black) pairs
They randomly paired 200 females (100 black, 100 red) to either a black or red male (of known morph genotype) in a visually isolated cage. Broods were reciprocally translocated permanently (within and between treatments) to control for genetic versus parentally derived environmental effects. After the first brood, the female was paired with a random male of the opposite morph (so each female bred twice, once with a compatible morph and once with an incompatible morph)
Females in mixed pairs produced broods with male-biased primary sex ratios: 82.1% males
Females in matched pairs produced an unbiased sex ratio: 45.9% males
In 20% of the eggs produced, there was no embryonic development, and therefore they were unable to sex those eggs. However, even if one assumes that all infertile eggs were female, there would still be an observed male-biased sex ratio in mixed-morph pairs: 60.3% males
Black females paired to red males who were experimentally blackened produced a sex ratio that did not differ significantly from equality: 55% males
Red females paired to experimentally blackened red males produced significantly more males: 72%
Individual females in mixed pairs produced significantly fewer eggs (3.391.07) than in matched pairs (5.670.89)
Females in mixed pairs also laid significantly smaller eggs (198.2314.12 mm3) than in matched pairs (227.0412.35 mm3)
When chicks (from both mixed and matched pairs) were fostered to nests of matched pairs they grew faster than foster chicks in mixed nests-- RM-ANOVA, F(1,158)=7.15,P=0.007,r^2=7.82-- irrespective of genetic origin-- F(1,158)=0.81, P=0.34
This was due to a per capita increase in maternal (but not paternal) provisioning to chicks in matched pairs--RM-ANOVA, female visit rate: F(1,159)=87.13, P<0.001, r^2=44.8; male visit rate: F(1,159)=0.04, P=0.83, r^2=6.4, N=324 broods
These affects were apparent when males were color-manipulated
Edited by Stagamancer, : No reason given.
"There are three kinds of lies: lies, damned lies, and statistics."
™ Version 4.2